The present invention relates to a method, and an article useful in the practice of such method, for altering the balance of a bowling ball to conform to a desired set of specifications. More specifically, the invention relates to an improved and simplified method of determining the location and size of a hole to be drilled in a bowling ball having predrilled grip holes and known balance characteristics in order to optimize such balance characteristics for a particular bowler.
Bowling balls are normally composed of a machineable, thermosetting plastic, comprising an inner core and a shell with a smooth, spherical surface. Although the plastic materials forming the core and shell are essentially homogeneous, a weight block having a density greater than that of the ball material is normally incorporated in the core, thereby placing the center of gravity at some point other than the center of the ball. Furthermore, removal of material by drilling the grip holes, i.e., two finger holes and a thumb hole, shifts the center of gravity to a location different from that of the undrilled ball, as well as changing the balance characteristics between pairs of adjacent ball hemispheres.
The action of a bowling ball as it travels down the lane is dependent upon the bowler's release, as well as the location of the weight block, and the location and amount of weight at the center of gravity. When a bowling ball is released in the usual manner, it tends to slide along the alley in its initial travel, then changing at some point, depending upon the previously noted factors, from a slide to a roll. The path of the ball is not usually the same during the slide and roll portions of the ball's travel. The change of direction in the transition from slide to roll is known as the "break" or "snap." The point in the ball's travel where the break begins, as well as the relative abruptness (i.e., whether a relatively gradual or a sharp break), also depend largely on the factors noted above. Of course, the coefficient of friction between the ball and lane also has a significant effect; thus, it is not uncommon for a bowler to have more than one ball, each having characteristics suited to the bowler's preference for the particular lane.
In order to achieve maximum striking power, it is necessary that the bowler use a consistent delivery or release, and that the ball have balance characteristics and a center of gravity located to provide an optimum break point for that particular release. By "balance characteristics" is meant the relative balance or imbalance of two adjacent hemispheres of the ball taken on each of three, mutually perpendicular, imaginary planes. These planes are in a specified relation to the position of the grip holes, as is well known to ball drillers and other advanced bowlers, and as explained in greater detail hereinafter.
Once a bowler has acquired sufficient experience and technique to develop a reasonably consistent release, the balance characteristics and center of gravity location of the ball must be established to optimize ball action, and thus score, for that particular release on a lane of known characteristics. The bowler's release, basically a combination of velocity, lift and spin imparted by the bowler, as well as the position of the weight block, will result in a specific "track," i.e., the circular area on the ball surface which contacts the lane during ball travel. The track concentrically surrounds the axis of rotation which, in virtually all cases, is disposed at an oblique angle with respect to the horizontal lane surface. The farther the weight block is removed from the track, the longer the ball will slide and the sharper it will break. Conversely, the closer the weight block is to the track, the earlier in its travel the ball will begin to roll and the more gradual the break.
The grip holes are drilled in the ball at a position relative to the weight block and the bowler's normal track to provide the general characteristics of slide, roll and break desired for the particular bowler's delivery or release. In order to optimize balance characteristics, it is then necessary to drill an additional hole, removing sufficient material from the ball to produce the previously mentioned relative imbalances between the three sets of ball hemispheres. The present invention is concerned with methods and means of determining the position on the surface of the ball for drilling the balancing hole and the amount of material to be removed to provide optimum ball action for the particular bowler using the ball.
For many years it has been the practice to weigh a bowling ball drilled with finger and thumb holes in each of three specified orientations on a device known as a dodo scale to determine the relative imbalance between three pairs of hemispheres. The location of, and amount of weight to be removed by, the balancing hole in order to change the known, i.e., the measured or "starting" weights, to the desired ending weights is then calculated. This operation has traditionally been performed by manual calculation involving comparison of each set of starting and ending weights with one another, and with the weights of other sets, and marking off calculated distances in specified directions from a reference point.
The calculations require considerable expertise and know-how in ball geometry and balance characteristics on the part of the ball driller. In order to simplify the process, and to render it more accurate, the mathematics of locating and sizing a balance hole, as well as other parameters of ball weight and drilling calculations, have been reduced to formulae and programmed into a pocket computer, as disclosed in U.S. Pat. No. 4,742,620, issued May 10, 1988 to R. C. Manker. Performance of the calculations in this manner, while considerably faster and possibly more accurate than the usual, manual method, requires access to and familiarity with operation of relatively expensive and technically sophisticated computer equipment.
It is an object of the present invention to provide an article of manufacture useful in implementing a novel and improved method of determining the location of a balance hole in a bowling ball having pre-drilled finger and thumb holes to optimize balance characteristics for a particular bowler.
An additional object is to provide an article of manufacture useful in implementing a novel and improved method of determining the amount of weight to be removed by a balance hole in a bowling ball in order to provide desired balance characteristics.
Another object is to provide an article of manufacture useful in implementing a method of determining side finger and top weights in a previously drilled bowling ball necessary to place the center of gravity in a desired location, which method may be performed easily and quickly, without the requirement of relatively expensive equipment such as computer hardware and custom software.
A further object is to provide a relatively inexpensive and simple article of manufacture which may be used with minimal training and experience to aid in determining values concerning the balance characteristics of bowling balls. Other objects will in part be obvious and will in part appear hereinafter.